1. Technical Field
The present invention relates to (3-oxoisoindolin-1-ylidine)propandinitrile derivatives as optically active chromophores and a method for preparing the derivatives.
2. Related Art
In a method for manufacturing an electro-optic device, an inorganic material, such as a semiconductor compound containing an element of group III-V in the periodic table, (e.g., LiNbO.sub.3, InP or GaAs), is used. Such an electro-optic device employing the inorganic material has been introduced into the market.
Recently, research into a method for manufacturing an electro-optic device using an organic chromophore has been conducted, and such electro-optic device is partially commercialized.
An electro-optic characteristic of the inorganic material is derived from cleavage and recombination of bonds between molecules. Electro-optic characteristics of the organic chromophore originate from polarization of the .pi.-electrons. Such an organic chromophore showing electro-optic characteristics based on the .pi.-electron resonance structure has good optical characteristics, such as a non-linear optical characteristic, compared to those of an inorganic material. Also, because the organic chromophore is mostly synthesized, various characteristics including a mechanical characteristic and stability to heat, oxygen and light can be optimized. In addition, it is easily applied to a manufacturing process for an electro-optic device based on a semiconductor manufacturing process.
In manufacturing an electro-optic device, including an electro-optic integrated circuit (OEIC), an optical waveguide device and a multi-chip module (MCM) device, a general semiconductor manufacturing process is applied. Thus, an optical material used for manufacturing the electro-optic device should have thermal stability for a required time at a temperature required for manufacturing a semiconductor.
The thermal stability of the optical material is closely related to the glass transition temperature, the thermal decomposition temperature, the thermal expansion coefficient and birefrigency. Thus, it is preferable to select an optical material appropriate for the above characteristics, as well as thermal stability.
However, known organic chromophores are not sufficient to secure heat resistance at temperatures required in manufacturing an electro-optic device. That is, the organic chromophore decomposes at temperatures for manufacturing the electro-optic device.
In order to solve the above problem, research into a method for improving heat resistance of the organic chromophore has been conducted. However, improving the heat resistance of the chromophore deteriorates its electro-optic characteristics, and complicates synthesis of the chromophore.
In addition, known organic chromophores cause a light loss in the near infrared light wavelength range, which is used for optical communications. The large optical absorption loss in the near infrared light wavelength range is due to the organic chromophore absorbing light in the near infrared light wavelength range. In general, light absorption of the organic chromophore in the near infrared light wavelength range is caused by overtone of harmonics according to stretching and deformation vibrations of the carbon-hydrogen (C--H) bond in the organic chromophore. Thus, using the organic chromophore as an optical material for an optical waveguide necessarily results in considerable optical loss. In order to reduce such optical loss, the light absorption wavelength region of the organic chromophore should be shifted to a longer wavelength region or a shorter wavelength region. To this end, a method for replacing hydrogen (H) of the C--H bond with fluoride (F) or heavy hydrogen (D) has been suggested.
The method for replacing H with D is not suitable for a material for use in an optical communications device employing a wavelength of 1,500 nm because a C--D bond has large optical loss in a wavelength of 1,500 nm. On the other hand, the method for replacing H with F has been verified as a method which enables minimization of light absorption loss at a wavelength range of 1,000.about.1,700 nm.